The Hydrodynamics of Phytoplankton Removal in Benthic Boundary Layers by Filter-Feeding Bivalves

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This project will continue experimental studies of the fluid mechanics of particle removal in turbulent boundary layers by suspension-feeding bivalve mollusks. During this award period, extensive measurements of velocity and concentration (solutes not particles) fields over two sets of model bivalves in a laboratory flume will be examined. The purpose of these experiments is to quantify the effects of near-bed hydrodynamics, i.e., the effects of both the excurrent jets and the turbulent boundary layer flow, on the flux of phytoplankton biomass from the water column to filter-feeding bivalves. The information obtained in the experiments will be used in formulating and operating numerical models of phytoplankton biomass dynamics in shallow estuaries, like San Francisco Bay. Experiments will also be conducted at the USGS flume facility to determine the effect of near bed hydrodynamics on bivalve feeding behavior. In particular, the effect of cross flow velocities on pumping rates, orientations, positions, and siphon heights of two species of bivalves commonly found in San Francisco Bay will be examined. This information is crucial to understanding the effects of concentration boundary layers on feeding strategies of bivalves and will be used to interpret the results of the physical measurements made in the new facility at Stanford. In its broadest terms, this project is focussed on understanding the effects of hydrodynamics processes on benthic-pelagic coupling in estuaries and shallow coastal waters. A major goal of the project is to translate that understanding into an ability to predict how the flow environment in a given body of water might affect the nature of this coupling for whatever phytoplankton assemblages and communities of benthic suspension feeders might be present. This is an excellent problem for illustrating how physical and biological processes are intertwined and how modelling might be used to develop an understanding of this coupling.